MUTATIONAL INTERACTIONS BETWEEN NEAR-UV RADIATION AND DNA DAMAGING AGENTS IN Escherichia coli: THE ROLE OF NEAR-UV-INDUCED MODIFICATIONS IN GROWTH AND MACROMOLECULAR SYNTHESIS

1983 ◽  
Vol 38 (1) ◽  
pp. 57-63 ◽  
Author(s):  
E. C. De Moraes ◽  
R. M. Tyrrell
Keyword(s):  
Escherichia Coli ◽  
Uv Radiation ◽  
Macromolecular Synthesis ◽  
Dna Damaging Agents

scholarly journals Involvement of recF, recO, and recR Genes in UV-Radiation Mutagenesis ofEscherichia coli

1998 ◽  
Vol 180 (7) ◽  
pp. 1766-1770 ◽  
Author(s):  
Ying-Hsiu Liu ◽  
Ann-Joy Cheng ◽  
Tzu-chien V. Wang
Keyword(s):  
Escherichia Coli ◽  
Uv Radiation ◽  
The Other ◽  
Ofescherichia Coli ◽  
Suppressor Mutation ◽  
Postreplication Repair ◽  
The Third ◽  
Recf Pathway ◽  
Lines Of Evidence

ABSTRACT The recF, recO, and recR genes were originally identified as those affecting the RecF pathway of recombination in Escherichia coli cells. Several lines of evidence suggest that the recF, recO, andrecR genes function at the same step of recombination and postreplication repair. In this work, we report that null mutations inrecF, recO, or recR greatly reduce UV-radiation mutagenesis (UVM) in an assay for reversion from a Trp− (trpE65) to a Trp+phenotypes. Introduction of the defective lexA51 mutation [lexA51(Def)] and/or UmuD′ into recF,recO, and recR mutants failed to restore normal UVM in the mutants. On the other hand, the presence ofrecA2020, a suppressor mutation for recF,recO, and recR mutations, restored normal UVM in recF, recO, and recR mutants. These results indicate an involvement of the recF,recO, and recR genes and their products in UVM, possibly by affecting the third role of RecA in UVM.

scholarly journals Genetic Evidence for the Requirement of RecA Loading Activity in SOS Induction after UV Irradiation in Escherichia coli

2006 ◽  
Vol 188 (14) ◽  
pp. 5024-5032 ◽  
Author(s):  
Ivana Ivančić-Baće ◽  
Ignacija Vlašić ◽  
Erika Salaj-Šmic ◽  
Krunoslav Brčić-Kostić
Keyword(s):  
Escherichia Coli ◽  
Uv Irradiation ◽  
Constitutive Expression ◽  
Recq Helicase ◽  
Sos Induction ◽  
Dna Damaging Agents ◽  
Lexa Repressor ◽  
Recbcd Enzyme ◽  
Dna Substrate

ABSTRACT The SOS response in Escherichia coli results in the coordinately induced expression of more than 40 genes which occurs when cells are treated with DNA-damaging agents. This response is dependent on RecA (coprotease), LexA (repressor), and the presence of single-stranded DNA (ssDNA). A prerequisite for SOS induction is the formation of a RecA-ssDNA filament. Depending on the DNA substrate, the RecA-ssDNA filament is produced by either RecBCD, RecFOR, or a hybrid recombination mechansim with specific enzyme activities, including helicase, exonuclease, and RecA loading. In this study we examined the role of RecA loading activity in SOS induction after UV irradiation. We performed a genetic analysis of SOS induction in strains with a mutation which eliminates RecA loading activity in the RecBCD enzyme (recB1080 allele). We found that RecA loading activity is essential for SOS induction. In the recB1080 mutant RecQ helicase is not important, whereas RecJ nuclease slightly decreases SOS induction after UV irradiation. In addition, we found that the recB1080 mutant exhibited constitutive expression of the SOS regulon. Surprisingly, this constitutive SOS expression was dependent on the RecJ protein but not on RecFOR, implying that there is a different mechanism of RecA loading for constitutive SOS expression.

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